Polypectomy snare devices

ABSTRACT

Polypectomy devices and methods for making and using polypectomy devices are disclosed. An example polypectomy device may include an elongate sheath having a proximal end region and a distal end region. A shaft may be slidably disposed within the sheath. A handle may be coupled to the proximal end region of the sheath. The handle may be designed to axially shift the shaft relative to the sheath. A snare may be coupled to the shaft. The snare may include a first region, a traction region, and a distal tip region. The first region may have a non-circular cross-sectional shape. The traction region may include a plurality of traction members. At a position between two adjacent traction members the snare may have a reduced cross-sectional area relative to the first region. The distal tip region may have a circular cross-sectional shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/663,568, filed Jul. 28, 2017, which claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 62/367,902, filed Jul. 28,2016, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to polypectomy devices including an end effector.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use. Some of these devices include guidewires, catheters,endoscopic devices, biopsy devices, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. A polypectomy device is disclosed. Thepolypectomy device, comprises: an elongate sheath having a proximal endregion and a distal end region; a shaft slidably disposed within thesheath; a handle coupled to the proximal end region of the sheath, thehandle being designed to axially shift the shaft relative to the sheath;a snare coupled to the shaft, the snare including a first region, atraction region, and a distal tip region; wherein the first region has anon-circular cross-sectional shape; wherein the traction region includesa plurality of traction members; wherein at a position between twoadjacent traction members the snare has a reduced cross-sectional arearelative to the first region; and wherein the distal tip region has acircular cross-sectional shape.

Alternatively or additionally to any of the embodiments above, the snareis formed from a monofilament wire.

Alternatively or additionally to any of the embodiments above, thenon-circular cross-sectional shape of the first region is D-shaped.

Alternatively or additionally to any of the embodiments above, the snarehas a first leg and a second leg, and wherein the non-circularcross-sectional shape of the first region is D-shaped along both thefirst leg and the second leg.

Alternatively or additionally to any of the embodiments above, along thefirst region the first leg and the second leg are designed to bearranged so that planar sides of the first leg and the second leg arepositioned adjacent to one another.

Alternatively or additionally to any of the embodiments above, thenon-circular cross-sectional shape of the first region is formed bygrinding a wire having a round cross-sectional shape.

Alternatively or additionally to any of the embodiments above, at leastsome of the traction members have a first side having a rounded outerprofile and a second side having a planar outer profile.

Alternatively or additionally to any of the embodiments above, all ofthe plurality of traction members have geometrically congruentcross-sectional shapes.

Alternatively or additionally to any of the embodiments above, at leastsome of the plurality of traction members have geometrically similarcross-sectional shapes.

Alternatively or additionally to any of the embodiments above, theplurality of traction members are formed by a plurality of annulargrooves formed along the snare.

Alternatively or additionally to any of the embodiments above, theplurality of traction members are formed by a helical groove formedalong the snare.

Alternatively or additionally to any of the embodiments above, thehelical groove varies in depth, pitch, or both along the length of thesnare.

Alternatively or additionally to any of the embodiments above, theplurality of traction members are formed by a helical member disposedalong the snare.

Alternatively or additionally to any of the embodiments above, the snareis formed from a tubular wire and wherein the plurality of tractionmembers are defined by a plurality of apertures formed through a sidewall of the tubular wire.

A polypectomy device is disclosed. The polypectomy device comprises: anelongate sheath; a shaft slidably disposed within the sheath; amonofilament snare wire coupled to the shaft, the snare wire having afirst end region, a first loop region, a first traction region, a firstdistal region, a nipple region, a second distal region, a secondtraction region, a second loop region, and a second end region; whereinthe first end region, the second end region, or both have a non-circularcross-sectional shape; wherein the first traction region, the secondtraction region, or both include a plurality of traction members;wherein the first distal region has a first reduced cross-sectional arearelative to the first end region; wherein the second distal region has asecond reduced cross-sectional area relative to the second end region;and wherein at least one of the first distal region, the nipple region,and the second distal region has a circular cross-sectional shape.

Alternatively or additionally to any of the embodiments above, thenon-circular cross-sectional shape of the first end region, the secondend region, or both is D-shaped.

Alternatively or additionally to any of the embodiments above, at leastsome of the traction members have a first side with a rounded outerprofile and a second side with a planar outer profile.

A method for manufacturing a polypectomy device is disclosed. The methodcomprises: machining a monofilament wire to form a snare wire, the snarewire having a first end region, a first loop region, a first tractionregion, a first distal region, a nipple region, a second distal region,a second traction region, a second loop region, and a second end region;wherein the first end region, the second end region, or both have anon-circular cross-sectional shape; wherein the first traction region,the second traction region, or both include a plurality of tractionmembers; wherein the first distal region has a first reducedcross-sectional area relative to the first end region; wherein seconddistal region has a second reduced cross-sectional area relative to thesecond end region; wherein at least one of the first distal region, thenipple region, and the second distal region has a circularcross-sectional shape; attaching the first end region and the second endregion to an elongate shaft; and disposing the elongate shaft within asheath.

Alternatively or additionally to any of the embodiments above, thenon-circular cross-sectional shape of the first end region, the secondend region, or both is D-shaped.

Alternatively or additionally to any of the embodiments above, at leastsome of the traction members have a first side with a rounded outerprofile and a second side with a planar outer profile.

A method for cutting a lesion is disclosed. The method comprises:disposing a snare about a lesion, the snare having a plurality oftraction members; engaging the lesion with the traction members;retraction at least a portion of the snare into a sheath; and cuttingthe lesion by applying electrosurgical energy to the snare.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a side view of an example medical device.

FIG. 2 is a cross-sectional view taken through line 2-2 in FIG. 1.

FIG. 3 is an alternative cross-sectional view.

FIG. 4 is an alternative cross-sectional view.

FIG. 5 is a top view of a portion of an example device.

FIG. 6 is a cross-sectional view taken through line 6-6 in FIG. 5.

FIG. 7 is a cross-sectional view taken through line 7-7 in FIG. 5.

FIG. 8 is a cross-sectional view taken through line 8-8 in FIG. 5.

FIG. 9 is a cross-sectional view taken through line 9-9 in FIG. 5.

FIG. 10 is a side view of a portion of an example medical device.

FIG. 11 is a perspective view of a portion of an example medical device.

FIG. 12 is a cross-sectional view of a portion of an example medicaldevice.

FIG. 13 is a partial cross-sectional view of a portion of an examplemedical device.

FIG. 14 is a side view of a portion of an example medical device.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (e.g., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used in connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

Colonic polypectomy generally corresponds to the removal of colorectalpolyps, for example, in order to prevent them from turning cancerous.Some polypectomy systems may include a snare that is engaged with apolyp. The polyp may be severed with the snare. For a number of reasons,it may be desirable to reduce buckling of the snare, reduced bending orflipping out of plane, and/or crossing of the legs of the snare.Disclosed herein are polypectomy devices that may include a snare. Thesnare is designed to have reduced buckling, reduced bending or flippingout of plane, and/or reduced crossing of the snare legs. Some of theseand other features are disclosed herein.

FIG. 1 illustrates an example polypectomy device 10. Device 10 mayinclude a sheath 12. A handle 14 may be coupled to sheath 12. Sheath 12and handle 14 may have a variety of different forms and/orconfigurations. For example, sheath 12 may have a length that issuitable to extend through an endoscope to a position within a bodylumen. This may include a body lumen along the digestive tract such asalong the small intestine and/or colon. Other body lumens may also beaccessed with sheath 12. A shaft 16 may be slidably disposed withinsheath 12. A snare 18 may be coupled to shaft 16. Snare 18 may generallybe designed to engage a body tissue such as a polyp and can be used tograb, sever, and/or remove polyps. In some instances, shaft 16 mayinclude an electrical connector so that electrical current (e.g.,cautery current) can be applied to snare 18.

Snare 18 may be formed from or otherwise include a wire 20. In at leastsome instances, wire 20 is a monofilament wire. For the purposes of thisdisclosure, a monofilament wire is understood to be a wire formed from asingle filament and/or a single monolith of material (e.g., a singularpolymer, a combination or blend of polymers formed into a singlefilament/monolith of material, a singular metal or metal alloy (e.g., anickel-titanium alloy), a combination of metals and/or alloys formedinto a single filament/monolith of material, etc.). In other instances,wire 20 may be formed from a plurality of filaments such as a pluralityof braided filaments. Wire 20 may be coupled to shaft 16, for example,at a crimp band 22. Other connections are contemplated. In at least someinstances, wire 20 may extend through sheath 12 to handle 14. Snare 18may have an opening size (e.g., ID) of about 10 to 55 mm. Wire 20 mayhave a diameter of about 0.005-0.050 inches, or about 0.008-0.040inches. The diameter of wire 20 may be chosen based on the length ofsnare. For example, a snare that is about 30 mm in length may utilize awire having a diameter of about 0.025 inches. It should be noted thatthe diameter and/or shape of wire 20 may change along the length thereofas described in more detail herein.

Along snare 18, wire 20 may include a first end region 24 a, a firstloop region 26 a, a first traction region 28 a, a first distal region 30a, a distal end region or nipple region 32, a second distal region 30 b,a second traction region 28 b, a second loop region 26 b, and a secondend region 24 b. The length and/or position of each region along snare18 may vary. For example, in some instances first end region 24 a and/orsecond end region 24 b may extend in a direction that is substantiallyparallel to the longitudinal axis of sheath 12. First loop region 26 amay extend from first end region 24 a to first traction region 28 a.First traction region 28 a may begin at the first (e.g., the mostproximal) of a plurality of traction members 34 disposed along snare 18.First distal region 30 a may begin at the last (e.g., the most distal)traction member 34. Nipple region 32 may extend between first distalregion 30 a and second distal region 30 b. In at least some instances,nipple region 32 projects distally to form the distal end of snare 18.Second traction region 28 b may extend along traction members 34. Secondloop region 26 b may extend between second traction region 28 b andsecond end region 24 b. The regions can be understood to be regions ofwire 20, regions of snare 18, or both.

Wire 20 may be thought of as defining two arms or legs of snare 18. Insome instances, the two arms may be substantially the same. For example,first loop region 26 a of a “first arm” of snare 18 may be substantiallythe same as second loop region 26 b, and so on. In other instances, thearms may differ. For example, first traction region 28 a may have afirst length and a first number of traction members whereas secondtraction region 28 b may have second length and a second number oftraction members where the lengths, number of traction members, or bothdiffer between arms. Other variations are contemplated for other regionsof snare 18.

As indicated above, first traction region 28 a, second traction region28 b, or both may include a plurality of traction members 34. The numberof traction member 34 may vary. In some instances, first traction region28 a, second traction region 28 b, or both may include 1, 2, 3, 4, 5, 6,7, 8, 9, 10, or more traction members 34. Regions 28 a/28 b may have thesame or a different number of traction members 34. The shape, form,spacing, and/or configuration of traction members 34 may vary. Forexample, in some instances traction members 34 may be oriented towardthe interior of snare 18. Traction members 34 may be equally spacedalong wire or may have a variable spacing (e.g., the density or numberof traction members 34 per unit length can be equal or vary). Tractionmembers 34 may have a pointed end, a square or rectangular end, orcombinations thereof. The height of tractions member 34 can also vary. Anumber of additional variations for tractions members 34 arecontemplated.

In at least some instances, at least a portion of snare 18, wire 20 mayhave a non-circular cross-sectional shape. Furthermore, thecross-sectional shape and/or dimension of wire 20 may vary along snare18. For example, FIG. 2 illustrates a portion of device 10 where it canbe seen that first end region 24 a and second end region 24 b have anon-circular cross-sectional shape. In this instance, first end region24 a and second end region 24 b have cross-sectional shape that issemi-circular or D-shaped. Other shapes are contemplated. For example,FIG. 3 illustrates a portion of device 110 where first end region 124 aand second end region 124 b are C-shaped. Other shapes are contemplatedincluding L-shaped. In other instances, an end region (e.g., end region224 as shown in FIG. 4) may have a polygonal cross-sectional shape suchas a triangular shape, a tear-drop shape, an oval shape, or the like.Other shapes are contemplated.

FIGS. 6-9 further illustrate how the shape, dimensions, andconfiguration of wire 20 may change along snare 18 (e.g., along thelength of snare 18). For example, along first loop region 26 a and/orsecond loop region 26 b, wire 20 may have a non-circular cross-sectionalshape such as a semi-circular or D-shape as depicted in FIG. 6. Such ashape may be the same or different from the cross-sectional shape of endregions 24 a/24 b. In at least some instances, the D-shaped of wire 20is formed by grinding, electron discharge machining (EDM), lasercutting, stamping, precision electrolytic machining (PEM), milling,coining, another suitable mechanism, and/or machining a wire with asubstantially round cross-sectional shape. For the purposes of thisdisclosure, any one or more of these processes (and/or other processes)may be understood to be “machining”. In FIG. 6, reference number 36 isintended to show the perimeter of wire 20 prior to grinding. However, inother instances, the cross-sectional shape of loop regions 26 a/26 b maybe formed by stamping. Other shapes are contemplated including L-shaped.

Wire 20 may also include a shape/size change in order to form tractionmembers 34. For example, FIG. 7 illustrates that along first tractionregion 28 a, wire 20 may include both a D-shaped portion and tractionmember 34 projecting therefrom. In some instances, traction member 34may have a planar end region 38. Like the shape of wire 20 along firstend region 24 a and/or first loop region 26 a, the shape of wire 20illustrated in FIG. 7 may be formed by grinding or another suitableprocess.

At a position along snare 18, the cross-sectional shape and/orsize/dimensions of wire 20 may change. The transition in shape/size mayoccur at a number of different locations. For example, the shape/size ofwire 20 may change along first loop region 26 a, at the junction offirst loop region 26 a and first traction region 28 a, along firsttraction region 28 a, or along first distal region 30 a. The transitionmay be gradual or more sudden/stepped. In some instances, at a locationbetween adjacent traction members 34, wire 20 may further transition inshape and/or dimensions. For example, FIG. 8 illustrates that at alocation 40 between two adjacent traction members 40, wire 20 may have aD-shaped cross-section. In this instance, the size of wire 20 is reducedrelative to the perimeter 36 of wire 20 through grinding, EDM, oranother suitable method. In other instances, wire 20 may be constantwithout a transition in size and/or shape.

FIG. 9 illustrates that along first distal region 30 a, wire 20 may havea substantially circular cross-sectional shape. The transition to around cross-sectional shape may occur at the junction between firsttraction region 28 a and first distal region 30 a, at a position alongfirst distal region 30 a, at the junction between first distal region 30a and nipple region 32, etc. The round cross-sectional shape may extendthrough nipple region 32 to at least a portion of second distal region30 b. In at least some instances, nipple region 32 may have a diameterof about 0.005-0.025 inches, or about 0.009 inches. It may be desirablefor nipple region 32 to be relatively short with a relatively wide base.This may aid in keeping snare 18 open during retraction of snare 18 intosheath 12. At some point along second distal region 30 b, wire 20 maytransition back to having a non-circular cross-section shape and furthertransition in a manner similar to the shape/sizes/transitions describedabove along first distal region 30 a, first traction region 28 a, andfirst end region 24 a.

In use, device 10 may be navigated to a position adjacent to a targetlesion (e.g., a sessile or flat lesion) or polyp. When suitablypositioned, snare 18 (e.g., a monofilament snare 18) may be opened andthe target lesion may be engaged by the traction members 34 (e.g.,and/or the first traction region 28 a and the second traction region 28b). Snare 18 may be at least partially retracted into sheath 12, whichmay at least partially close snare 18 and capture the lesion. In someinstances, this may include applying a downward force with a portion ofwire 20 such as, for example, first loop region 26 a and/or second loopregion 26 b. The lesion may be cut with electrosurgical energy (e.g.,application of electrocautery energy to wire 20) and/or by mechanicalforce applied by snare 18 (e.g., first distal region 30 a and/or seconddistal region 30 b).

FIG. 10 illustrates a portion of another example device 310 that may besimilar in form and function to other devices disclosed herein. In thisexample, wire 320 may include a plurality of traction members 334 formedby annular grooves along wire 320. Grooves 334 may be formed by grindingor another suitable process. Grooves 334 may be disposed along atraction region of an example snare such as those snares disclosedherein.

FIG. 11 illustrates a portion of another example device 410 that may besimilar in form and function to other devices disclosed herein. In thisexample, wire 420 may include helical traction members 434. Tractionmember 434 may be threaded onto or otherwise disposed along wire 420.Traction member 434 may be disposed along a traction region of anexample snare such as those snares disclosed herein.

FIG. 12 illustrates a portion of another example device 510 that may besimilar in form and function to other devices disclosed herein. In thisexample, a “tubular wire” or tube 520 may be utilized. Tube 520 mayinclude a lumen 542. In some instances, one or more traction members 534may be formed in tube 520 as side holes or apertures as shown in FIG.13. Tube 520 may be used for example snares such as those snaresdisclosed herein. In some instances, tube 520 may be tapered orotherwise include one or more tapered sections (e.g., such as a distaltapered section).

FIG. 14 illustrates a portion of another example device 610 that may besimilar in form and function to other devices disclosed herein. In thisexample, wire 620 may include a helical groove 634 formed therein.Helical groove 634 may form a plurality of traction members. In at leastsome instances, the pitch, depth, or both of helical groove 634 may varyalong the length of wire 620. In addition, the shape and/or dimensionsof wire 620 may also change.

The materials that can be used for the various components of polypectomydevice 10 (and/or other polypectomy devices disclosed herein) and thevarious wires, snares, sheaths, etc. disclosed herein may include thosecommonly associated with medical devices. For simplicity purposes, thefollowing discussion makes reference to sheath 12 and other componentsof device 10. However, this is not intended to limit the devices andmethods described herein, as the discussion may be applied to othersimilar tubular members and/or components of the devices disclosedherein.

Sheath 12 and/or other components of device 10 may be made from a metal,metal alloy, polymer (some examples of which are disclosed below), ametal-polymer composite, ceramics, combinations thereof, and the like,or other suitable material. Some examples of suitable polymers mayinclude polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

In at least some embodiments, portions or all of device 10 may also bedoped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of device 10 in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, polymer material loadedwith a radiopaque filler, and the like. Additionally, other radiopaquemarker bands and/or coils may also be incorporated into the design ofdevice 10 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility is imparted into device 10. For example, device 10, orportions thereof, may be made of a material that does not substantiallydistort the image and create substantial artifacts (e.g., gaps in theimage). Certain ferromagnetic materials, for example, may not besuitable because they may create artifacts in an MRI image. Device 10,or portions thereof, may also be made from a material that the MRImachine can image. Some materials that exhibit these characteristicsinclude, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g.,UNS: R30003 such as ELGILOY®, PHYNOX®, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nitinol, and the like, and others.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A polypectomy device, comprising: an elongatesheath having a proximal end region and a distal end region; a shaftslidably disposed within the sheath; a handle coupled to the proximalend region of the sheath; a snare coupled to the shaft, the snareincluding a first region having a first cross-sectional shape, atraction region including a plurality of traction members, and a distaltip region; wherein at a position between two adjacent traction membersthe snare has a second cross-sectional shape that is geometricallysimilar to the first cross-sectional shape and has a reducedcross-sectional area relative to the first region; and wherein thedistal tip region has a circular cross-sectional shape.
 2. Thepolypectomy device of claim 1, wherein the snare is formed from amonofilament wire.
 3. The polypectomy device of claim 1, wherein thefirst cross-sectional shape is a non-circular shape.
 4. The polypectomydevice of claim 3, wherein the snare has a first leg and a second leg,and wherein the first cross-sectional shape of the first region isnon-circular along both the first leg and the second leg.
 5. Thepolypectomy device of claim 3, wherein along the first region the firstleg and the second leg are designed to be arranged so that planar sidesof the first leg and the second leg are positioned adjacent to oneanother.
 6. The polypectomy device of claim 1, wherein the firstcross-sectional shape of the first region is formed by machining a wirehaving a round cross-sectional shape.
 7. The polypectomy device of claim1, wherein at least some of the traction members have a first sidehaving a rounded outer profile and a second side having a planar outerprofile.
 8. The polypectomy device of claim 1, wherein all of theplurality of traction members have geometrically congruentcross-sectional shapes.
 9. The polypectomy device of claim 1, wherein atleast some of the plurality of traction members have geometricallysimilar cross-sectional shapes.
 10. The polypectomy device of claim 1,wherein the plurality of traction members are formed by a plurality ofannular grooves formed along the snare.
 11. The polypectomy device ofclaim 1, wherein the plurality of traction members are formed by ahelical groove formed along the snare.
 12. The polypectomy device ofclaim 11, wherein the helical groove varies in depth, pitch, or bothalong the length of the snare.
 13. The polypectomy device of claim 1,wherein the plurality of traction members are formed by a helical memberdisposed along the snare.
 14. The polypectomy device of claim 1, whereinthe snare is formed from a tubular wire and wherein the plurality oftraction members are defined by a plurality of apertures formed througha side wall of the tubular wire.
 15. A polypectomy device, comprising:an elongate sheath; a shaft slidably disposed within the sheath; amonofilament snare wire coupled to the shaft, the snare wire having afirst end region, a first loop region, a first traction region, a firstdistal region, a nipple region, a second distal region, a secondtraction region, a second loop region, and a second end region; whereinthe first traction region includes a plurality of traction members;wherein the first distal region has a first reduced cross-sectional arearelative to the first end region; and wherein the first distal regionhas a first section having a non-circular cross-sectional shape, asecond section having a circular cross-sectional shape, and a junctionwhere the non-circular cross-sectional shape of the first sectiontransitions to the circular cross-sectional shape of the second section.16. The polypectomy device of claim 15, wherein the first end region,the second end region, or both have a non-circular cross-sectionalshape.
 17. The polypectomy device of claim 15, wherein at least some ofthe traction members have a first side with a rounded outer profile anda second side with a planar outer profile.
 18. A method formanufacturing a polypectomy device, the method comprising: machining amonofilament wire to form a snare wire, the snare wire having a firstend region, a first loop region, a first traction region, a first distalregion, a nipple region, a second distal region, a second tractionregion, a second loop region, and a second end region; wherein the firstdistal region has a first section having a non-circular cross-sectionalshape and a second section having a circular cross-sectional shape;forming a junction along the first section where the non-circularcross-sectional shape of the first section transitions to the circularcross-sectional shape of the second section; attaching the first endregion and the second end region to an elongate shaft; and disposing theelongate shaft within a sheath.
 19. The method of claim 18, wherein thefirst end region, the second end region, or both have a non-circularcross-sectional shape.
 20. The method of claim 18, wherein the firsttraction region includes a traction member having a first side with arounded outer profile and a second side with a planar outer profile.